Multioffice telephone system



Jne 23, 1931. v. s. THARP MULTIOFFICE TELEPHONE SYSTEM Filed April so.195o Patented `.lune 23, 193i STATES PATENT @FFECE VICTOR SkfTHARP, OFELMHRST, ILLINOIS, .ASSIGNOR T0 RESERVE HOLDING COM- IPANY, OF CHICAGO,ILLINOIS, A COBPORATON 0F DELAY-.TARE

MULTIOFFICE TELEFHONE SYSTEM i Application lcd April 30, 1930. SerialNo. 448,701.

This invention relates to improvements in Vmulti- Gilice telephonesystems, particularly toimproved trunking arrangements and apparatus forinterconnecting the various oftices ofsuch systems.

' Special service trailic such as toll recording,information',complaint, etc., are ordinarily handled at' a central pointin multin cnice 'telephone systems. Vhen the system l0 comprises anumber of automatic exchanges of relatively small size it is oftenimpractical to provide a separate-switchboard for each type of serviceand for this reason aswitchboard for the combined special servicetrailic l"'5 is provided.. An alternativemethodisto route all specialservice traiiic over the regular interoljlice trunks to a manualexchange or toll switchboard.V This latter arrangement is particularlydesirable for small systems in 0. which the volume of traiiic isinsuiiicient to warrant the services of -a separate operator.There.is,`however, the disadvantage that iniportant trunk lines are tiedup and an additional load is 4imposed on the toll operator 25 during thebusy hours of the day.

Y One ofk the main objects of this invention is the provision of a.special service trunking system which combines the advantageous featuresof beth ofthe above methods without including their disadvantages. Thisend is attained` byJ providing a switrchboardof which l the specialservice trailc of agroup o small automatic exchanges is handled duringthe period of heavy traic together with vspecial trunking apparatuswhich routes this traiiic to a manual oi'hce or toll board during theperiod of light trattic.

The various features of the kinvention whichrelate principally to newand improved vapparatus for providing the above discussed Vtype otlservice will be described in detail alongfwiththe operation of thevarious circuits involved.

A system disclosing the invention in one of its narrow aspects is shownin the accompanying single ligureotdrawing. This system comprises threeoliices designated, respectively, oiliceA,'oiiiceB and office C. Of-

9 fices A and B are assumed to be of any well 50.- known` typerofautomatic exchange. The

switching apparatus ordinarily provided for such exchanges is well knownin the art and, since it forms no part of the invention, it has not beenshown in detail. The two automatic exchanges are connected by trunklines of which a representative trunk line T is shown. This particulartrunk line is arranged for two-way service and terminates in a two-wayrepeater at otiice A and in trunk rela-y group TTR at oilic'e B. Thethree branches ot' the trunk at o'liice- B extend, respectively, to jackJ at the special service switchboard, to the banks of finder switch F,and to the banks of local selectors in the exchange. At the switchboard,the busy visual signal S, call lamp L, and key K are associated with andindividual to the jack J.

Oiiice C is assumed to be a toll board o r manual office which will beattended at all times. This oliice is connected by trunks, such as thetrunk lin'e Tl, with oliice B at which it terminates in a. repeater Thetrunk line may be of any well known type tor example, such as the trunklines disclosed in the United States Patent No. 1,571,966 to Ray. Whensuch trunk lines are employed repeater R and trunk circuit Rl willcorrespond, respectively, to repeater R and the trunk circuit associatedwith trunk line X, of the above referred to patent.

The trunk line which is ordinarily provided with two branches extending,respectively, to an incoming selector or line switch and to the banksvof selec-tors, is modified in this case by the provision of a thirdbranch terminating 4in finder switch F. This additional branch ismult-ipled directly with the branch extending to the selector banks anddoes not necessitate any alterations in the repeater circuit. In theevent that one-way trunks are employed in the system, the finder switchF is associated with an outgoin trunk in substantially the same mannerin the present disclosure.

The number of trunks equipped with finder switches will depend entirelyupon the volume of tratiic. A Vgroup of starting relays SR is providedfor the linder switch group and trunks has not been shown in detailsince controls the operation oit these switches by means ofthe usualchain circuit.

Speciall service trunks accessible to the local selectors in oilice Bterminate in trunk relay groups, such as the group LTR, of whichbranches eXtend to the switchboard and to the banks of the finderswitchV VThe switchboard Vapparatus terminating corresponds in everyrespect tothe apparatus terminati-ng the trunk line r designations havebeen applied to carre! lsponding conductors of the branches of bothVincoming and local trunks.

Trunk calls .from olilfe A will normally be extendedv to the voperatorat oiiiceB wha will complete them in they usual way over operatorsswitch train (not shown). However, when the switchboard at oliice l beleft unattended the-transfer key, such a vl'ev K, ofeach trunk line willbe actuated,t

by placing the finder switches F in service.

Underthesev conditions, calls overeith r the incoming or local trunkswill cause ai finder switch to connect-.with the calling trunk anc.extendthe call over the trunk line T1 Vte the manualoiice or Jtoll boardat which it will be completed in the usual way. 1

The foregoing brief description sets torta the broad object of theinvention. ln order 'to better illustrate the various features oi theinvention the operations involved in setting up connections will now bedescribed in detail. v, Y

The Vordinary manner of handling. calls from o'tlice Awill be consideredfirst. he calling subscriber dials thespecial service code and isconnected with a trunk line, such as T, in the usual manner. A loopcircuit is completed for the trunk at the outgoing re.- peater and linerelay 11, which isbridged across conductorsl and 2 oic the trunk,operates. YRing-back-tone is applied'to the'tijunk yinto a toll line orservice 'trunkr and j ringing or dialling in the well 'known A by way ofthe lower armature of relay-11, and ground, by way or the upperarmatureot this relay, is connected to signal. conductor 5 which extendsvthrough normallyfciosed: contacts of key K to lamp L. LampL lights 'tonotify the operator of an incoming call.`

cord

Y' V1Whenle'aving the position unattended, the

'op'erator will actuatethe ytransfer key K of Similar I each trunkV lineterminating in the switchboard.y All incoming calls over the trunk lineT, under these conditions, will operate relay 11 as in the previousinstance. The signal conductor 5, however, has been extended through theoperated contacts of keyrK to relay 22 which operates under thecontrolof relay 11. Relay 11 also removes ground from conductor 10, therebymarkingthe trunk line as calling in the banks ofthe inder switch.

Relay 22 on operating completes va circuit through thevnormally-closedcontacts of relay 31'to relay' 33 which operates.y Relay33 at its upperV armature completes a circuit for relay 32. andsteppingmagnet 38 in series, and at ,its lower armature connects test wiper 36'in parallel Vwith relay 32. Non-'calling trunk lines are marked in thebanks of the inderbyy groundvon the associated test contacts throughback contacts of relays, Vsuch as` relays 11 and .12. In case wiper 136is standing on ythe Vcontacts of a non-calling i trunk the groundthereon fwill consequently shunt relay 32 and prevent it from operating.Magnet 38, however, Vwill operate, step the wipers aheadKA to .the nextset of contacts and open its ownV circuit at the interrupter springs.This operation is repeated until the calling trunk is found which ismarked by the absence of ground onk the test contact. Relay32 will nolonger be shunted and will operate in series with magnet 38. The magnet,however, does not operate due to the high resistance ofV the relay.Relay 32 connects the talking conductors torepeater rRat its outerarmatures, disconnects Vrelay 3l from `the release'trunk conductor atarmature 39 and by means ofthat armature andarinature 40 .extends therelease trunk conductor through to wiper 35 and completes a lockingcircuit for itself, closes a circuit for lthe'lower winding of relay 31kat armature 41 and disconnects test wiper 36 at]v armature 42.

Ground from the upperv armature of relay 33 `extends by wayofar1naturef40and wiper 35 through contacts offrelay 11 to the lower.winding of relay 12, and this relay operates to connect the talkingconductors'of the trunk through Vas in thev previous instance. Thecallingloop is thereby extended over wipers 34- and'V 37 to the linerelay of. repeater R which operates. Repeater R then returns a holdingground on the release trunk in the usual way `to maintain relay 32 offinder switch FV and relay 12 othel trunk relay group operated. Relay 31ori-'operating disconnects relay 33: from the startingconduc` tor andextends this'conductor tothe next switch of the train. VRepeaterR'tunctions in the well knownmanner to extend the call Y' over the trunkand operates asignal at the y switchboard in vwhich the'trunkterminates.

ins

At the end of the-conversation the calling subscriber hangs up and openstheploop circuit, thereby releasingy the line relay of the lilrepeater.y Groundis removed from the release trunk and relays 32 of theinder switch and 120i the trunk relay grou-p restore to normal.

lt. will be noted that the starting conductor from relay group SR isshown extending through contacts of a relay ot'switch F, and asindicated by the dotted line through similar contactsot' correspondingrelays of other finder switches, to relay 21. The relay 31 which isV no`mally connected to the release trunk conductor of the outgoing trunkoperstes whenever the associated trunk is busy. When all outgoing trunksare busy, an incoming call will operate startingv relay 22 in the usualmanner and this in turn will close a circuit for relay 2l. Relay 21 onoperating ldisconnects the ring-back-tene from conductor9 and connectsthe busy tone thereto in- This tonewill be audible to the callingsubscriber whois thereby informed that no trunks are available at thistime. Should the subscriber maintain the connection until atrunk becomesidle, the finder associated with such trunk will immediately connectwith the calling trunk and extend the call in the previously describedmanner.

Loca-l calls to the special service operator are handled insubstantially the same manner as trunk calls. Thcsubscriber dials thecode assigned to the operator and a local selector connects with an idletrunk such as the one terminating in trunk relay group LTR y Vwhereonline relay 5l operates over the calling subscribers loop Relay 5lgrounds the signal. conductor 5 which corresponds to conductor 5 of theincoming trunk and extends through contacts of a keysuch as K, to asignal lamp, such as lamp L, associated with the local trunk.` Relay 51also connects a holding ground to the release trunk, removes ground fromconductor l0 to markv the trunk as calling in the banks et the finderswitches .and prepares the switchingy circuit by closing a point in thecircuit of relay 52. In case the switchboard lis attended and key K isnormal, the associated signal lamp will light, as in the previousinstance. When the operator answers the call, ground. from the jackcontacts will be extended over conductor 7 to operate relay 53.` Relay53 on operating disconnects the ring-backtone from the trunk at itslower armature and extends the talking conductors of the trunk throughto the tip and ring contacts of the jack by way of conductors 3 and 4,removes ground from the starting lead, and connects an additionalgroundV to the release trunk conductor. It will be noted in this casethat the line relay is not disconnected when the operator answers, butcontinues to feed talking battery to the calling subscriber'.

A call coming in over the local trunk with. the special serviceswitchboard unattended will be forwarded to the manual oflice in muchthe same way as the previously described trunk calls.- Ground on thesignal conductor 5 instead of operating the associated call lamp at theswitchboard will operate starting relay 22. Relay 22 will start an idlefinder switch to hunting as in previously described connections, theswitch hunting for a trunk marked by the a sence ot ground on its testcontacts, such as the one terminating conductor 10. When the callingtrunk is connected with, relay 52 operates over a circuit includingcontacts of relay 5l, wiper 35 oi' the finder switch, armature l0 oi theswitching relay, and the upper armature ot starting relay 33 ot thelinder switch. Relay 52 closes a locking circuit for itself independentot the contacts of relay 5l, connects a holding ground -to the releasetrunk conductor, and disconnects the talking conductors of the trunkfrom line relay 5l and extends them through without condensers to thewipers 34 and 37 of the finder switch. Finder switch F operates inexactly the same manner as was previously described and the repeater Rreturns the ground on the release trunk to hold up switching relay 32and relay 52 in the usual manner.

lin the event oit a call coming in on a local trunk when all finderswitches are busy the calling-subscriber will receive a busy tone in thesame manner as previously described for trunk call. The release of theconnection is accomplished in the same manner as the release of a trunkconnection.

lVhat is claimed is:

l. In a telephone system, an exchange, incoming trunk lines and outgoingtrunk lines terminating in said exchange, a manual switchboard at theexchange for answering calls over said incoming trunk lines, andswitching mechanism at said exchange for automatically extendingincoming trunk callsover said outgoing trunk linesI whei saidswitchboard is unattendec.

2. In a telephone system, three exchanges,

trunk lines extending from the first exchange to a manual switchboard atthe second exchange, other trunk lines extending from the secondexchange to a manual switchboard at the third exchange, means in thefirst exchange for extending calls over said first trunk lines to theswitchboard at the second exchange, and automatic means at the secondexchange tor further extending such calls over said other trunk lines tothe switchboard at the third exchange when the switchboard at the secondexchange is unattended.

3. ln a telephone system, three exchanges, trunk lines extending fromthe first exchange to a manual switchboard at the second exchange, othertrunk lines extending from the second exchange to a manual switchboardat the third exchange, `finder switches terminating said other trunklines at the vsecond exchange and having access to said first trunl:

line, and a key at said first switchboard for each of said first trunklines for rendering said finder switches effec-tive to connect with acalling one of 'said first'trunl lines when vone 01"' said incomingtrunk lines foroperating either the Lassociated signal or ksaid relaydepending on whether the associated heT is normal or operated. I .L

5. yln a telephone system, an incoming trunlrhne terminatine` '1n amanual-switchb Y -I e A n a board an out oinfr trunx line terminatin ina finder switch having access to said incoming trunk line, a startingrelay for said switch, a signalconductor grounded responsive to a. callover said incoming trunk line, a signal normally connected to saidconcluetor., and a hey for disconnecting said conductor from said signaland tor connecting it to said relay.

6. In a telephone system,incoming trunk lines terminating in a manualswitchboard,

outgoing trunk lines terminating in finder switches having access tosaid incoming trunk f' lines, a common starting relay for said switches,a signal conductor for each incom-A ing trunk line adapted to begrounded responsive to aV call over the associated trunk line, a signalnormally connected to each conductor, and a key `for each incoming trunkline for disconnecting the associated conductor from its correspondingsignal and Vi'cr connecting it to said common relay.

7. 'ln av telephone system comprising three "rially related exchanges,interconnecting .nh lines, manual? switchboards in the second andthirdexchanges, avsignal at the switchboard in the second'exchange adapted tooperate in response to a call over a trunk line from the Erst exchange,s itching mechanism in the second exchange adapted to automatically'extend incoming trunk calls vtrom the firstA exchange to theswitchboard in the third exchange, .and a key atthe switchboard in thesecond exchange for rendering foi-her i signal or switching mechav nismeffective. Y

8. ln atelephon'e system, a tandem exchange, incoming and; outgoingtrunk lines terminating in said exchange, finder switches associatedwith said outgoing trunk lines,

means responsive to a call over an incoming trunk line for operating theswitch associated with anv idleoutgoing ,trunk line to connect theY sameto the calling trunk line,

f and means responsive to a call 'over an incomtrunk line for applying abusy tone thereto'pro'viding no vidle outgoing trunk line is available.Y

. 9. In a'telephone system, incoming trunk lines terminating in a manualswitchboard, outgoing trunk lines terminating inl finder switches havingaccess to said incoming trunk lines,l a4 signal at the switchboard foreach incoming tr'unl; line, a lstarting relay for causingl the finderswitch associated-with an idle outgoing trunk line to operate andconnect with a calling incoming trunk line, a key at the switchboard foreach incoming trunk line for rendering either the associated signal or:said relay effective, andY means controlled by said relay for applying abusy tone to a callin@ incomin trunk line when alloute I l second YandVthird exchanges, a signal at the switchboard'V in the second exchangeoperated responsive .to an incoming lcall from the i'irst exchange,automaticrswitches in the second exchange operated responsive to anincoming callffrom the ii 1st exchangefto extend such call to theswitchboardin the third exchange when the switchboard in the secondexchange isunattended, and means at the second exchange operatedresponsive toan incoming call Yfrom the rst' exchange for 'returning abusy tone to the calling subscriber when the switchboard in the secondexchange is unattended and all'gtrunks between thepsecond and thirdexchanges are busy. y y

Y l1. In a telephone system, a trunk line accessible at one end toautomatic switches and vhaving two normally disconnected branches at theotherend, a manual switchboard terminating one of said branches, nderswitches having access to the other of said branches', a line relaybridgedacross the talking conductors ofthe trunk line Voperativeresponsive to ,the extension of a'v call to the trunk line for eithersignalling the operator at said switchboard .or for initiating theoperation of oneY of said Vfinder switches, means vresponsive providedthe call is answered from the switchboard for connecting the trunk linevto said first branch, and means yresponsive provided Y one of lsaid'finder mynname this 28th day of April, A. 13.71930.

y. vieron s. maar.

